scholarly journals Bottom-up and top-down effects of temperature on body growth, population size spectra and yield in a size-structured food web

2021 ◽  
Author(s):  
Max Lindmark ◽  
Asta Audzijonyte ◽  
Julia Blanchard ◽  
Anna Gårdmark
Keyword(s):  
Food Web ◽  
Growth Rates ◽  
Temperature Effects ◽  
Size Structure ◽  
Metabolic Effects ◽  
Young Fish ◽  
Top Down ◽  
Bottom Up ◽  
Effects Of Temperature ◽  
Size At Age

AbstractResolving the combined effect of climate warming and exploitation in a food web context is key for predicting future biomass production, size-structure, and potential yields of marine fishes. Previous studies based on mechanistic size-based food web models have found that bottom-up processes are important drivers of size-structure and fisheries yield in changing climates. However, we know less about the joint effects of ‘bottom-up’ and ‘top-down’ effects of temperature: how do temperature effects propagate from individual-level physiology through food webs and alter the size-structure of exploited species in a community? Here we assess how a species-resolved size-based food web is affected by warming through both these pathways, and by exploitation. We parameterize a dynamic size spectrum food web model inspired by the offshore Baltic Sea food web, and investigate how individual growth rates, size-structure, relative abundances of species and yields are affected by warming. The magnitude of warming is based on projections by the regional coupled model system RCA4-NEMO and the RCP 8.5 emission scenario, and we evaluate different scenarios of temperature dependence on fish physiology and resource productivity. When accounting for temperature-effects on physiology in addition to on basal productivity, projected size-at-age in 2050 increases on average for all fish species, mainly for young fish, compared to scenarios without warming. In contrast, size-at-age decreases when temperature affects resource dynamics only, and the decline is largest for young fish. Faster growth rates due to warming, however, do not always translate to larger yields, as lower resource carrying capacities with increasing temperature tend to result in declines in the abundance of larger fish and hence spawning stock biomass – the part of the population exposed to fishing. These results show that to understand how global warming impacts the size structure of fish communities, both direct metabolic effects and indirect effects of temperature via basal resources must be accounted for.

Trophic Relationships in Freshwater Pelagic Ecosystems

1986 ◽  
Vol 43 (8) ◽  
pp. 1571-1581 ◽  
Author(s):  
Donald J. McQueen ◽  
John R. Post ◽  
Edward L. Mills
Keyword(s):  
Food Web ◽  
Trophic Status ◽  
Size Structure ◽  
Trophic Relationships ◽  
Top Down ◽  
Eutrophic Lakes ◽  
Bottom Up ◽  
Coefficients Of Variation ◽  
Step Down ◽  
Pelagic Ecosystems

Relative impacts of bottom-up (producer controlled) and top-down (consumer controlled) forces on the biomass and size structure of five major components of freshwater pelagic systems (piscivores, planktivores, zooplankton, phytoplankton, and total phosphorus availability) were estimated. Predictions that emerge are (1) maximum biomass at each trophic level is controlled from below (bottom-up) by nutrient availability, (2) this bottom-up regulation is strongest at the bottom of the food web (i.e. phosphorus → phytoplankton) and weakens by a factor of 2 with each succeeding step up the food web, (3) as energy moves up a food web, the predictability of bottom-up interactions decreases, (4) near the top of the food web, top-down (predator mediated) interactions are strong and have low coefficients of variation, but weaken with every step down the food web, (5) variability around the bottom-up regressions can always be explained by top-down forces, and (6) interplay between top-down and bottom-up effects changes with the trophic status of lakes. In eutrophic lakes, top-down effects are strong for piscivore → zooplankton, weaker for planktivore → zooplankton, and have little impact for zooplankton → phytoplankton. For oligotrophic lakes, the model predicts that top-down effects are not strongly buffered, so that zooplankton → phytoplankton interactions are significant.

scholarly journals Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes

2013 ◽  
Vol 71 (2) ◽  
pp. 406-416 ◽  
Author(s):  
T. O. M. Reilly ◽  
H. M. Fraser ◽  
R. J. Fryer ◽  
J. Clarke ◽  
S. P. R. Greenstreet
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Levels ◽  
Top Down ◽  
Bottom Up ◽  
Control Processes ◽  
Top Predators ◽  
Environmental Status ◽  
Fish Predators ◽  
Firth Of Forth

Abstract Reilly, T. O. M., Fraser, H. M., Fryer, R. J., Clarke, J., and Greenstreet, S. P. R. 2014. Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes. – ICES Journal of Marine Science, 71: 406–416. Proposed indicators for the Marine Strategy Framework Directive (MSFD) food webs Descriptor focus on structural elements of food webs, and in particular on the abundance and productivity of top predators. However, the inferences that can be drawn from such indicators depend on whether or not the predators are “bottom-up limited” by the availability of their prey. Many seabird populations appear to be “bottom-up limited” so that variation in their reproductive success and/or abundance reflects changes in lower trophic levels. Here we find that gadoid fish predators off the Firth of Forth, southeast Scotland, do not appear to be “bottom-up limited” by the biomass of their main prey, 0-group sandeels; gadoid biomass and feeding performance was independent of sandeel biomass. Variability in food web indicators based on these gadoid predators seems to impart little insight into underlying processes occurring at lower trophic levels in the local food web. The implications of this in terms of how the currently proposed MSFD food web indicators should be used and interpreted are considered, and the ramifications in terms of setting targets representing good environmental status for both fish and seabird communities are discussed.

scholarly journals Nitrogen fixation in mesoscale eddies of the North Pacific Subtropical Gyre: patterns and mechanisms

2021 ◽  
Author(s):  
Mathilde Dugenne ◽  
Mary R Gradoville ◽  
Matthew J Church ◽  
Benedetto Barone ◽  
Samuel T Wilson ◽  
...  
Keyword(s):  
Growth Rates ◽  
North Pacific ◽  
Mesoscale Eddies ◽  
Subtropical Gyre ◽  
Positive Anomaly ◽  
North Pacific Subtropical Gyre ◽  
Top Down ◽  
Bottom Up ◽  
The North ◽  
The North Pacific

Recent studies suggest that mesoscale eddies may support elevated dinitrogen (N2) fixation rates (NFRs) and abundances of N2-fixing microorganisms (diazotrophs), yet the strength and mechanistic underpinnings of this trend are not fully understood. We explored the relationships among NFRs, cyanobacterial diazotroph abundances, and environmental conditions of mesoscale eddies by sampling three pairs of eddies of opposite polarity in the North Pacific Subtropical Gyre. Using the Hawaii Ocean Time-series for historical context, we found that NFRs were anomalously high (up to 18.6 nmol N L-1 d-1) in the centers of two anticyclones. The highest NFR was linked to a positive anomaly in Crocosphaera abundance. To unravel the main processes and players, we used high-resolution abundance data, metatranscriptomes, deck-board incubations, and population models to evaluate three mechanisms for each diazotroph population: bottom-up control, top-down control, and physical control. Based on cell division and grazing rate estimates, Crocosphaera anomalies appeared to be partially driven by both bottom-up control (due to elevated surface phosphate concentration promoting high growth rates) and top-down control (reduced grazing pressure from putative predators). In contrast, although large, buoyant Trichodesmium and symbionts of diatoms (Richelia ) appeared to have accumulated at the fronts between cyclonic and anticyclonic eddies, they had lower growth rates and contributed less to bulk NFRs. Together, the interplay of these three complex mechanisms may explain reports of elevated diazotroph abundances and NFRs associated with anticyclones and eddy fronts.

scholarly journals The meaning of functional trait composition of food webs for ecosystem functioning

2016 ◽  
Vol 371 (1694) ◽  
pp. 20150268 ◽  
Author(s):  
Dominique Gravel ◽  
Camille Albouy ◽  
Wilfried Thuiller
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Functional Diversity ◽  
Ecosystem Functioning ◽  
Functional Trait ◽  
Plant Ecology ◽  
Functional Composition ◽  
Top Down ◽  
Bottom Up ◽  
Functional Trait Diversity

There is a growing interest in using trait-based approaches to characterize the functional structure of animal communities. Quantitative methods have been derived mostly for plant ecology, but it is now common to characterize the functional composition of various systems such as soils, coral reefs, pelagic food webs or terrestrial vertebrate communities. With the ever-increasing availability of distribution and trait data, a quantitative method to represent the different roles of animals in a community promise to find generalities that will facilitate cross-system comparisons. There is, however, currently no theory relating the functional composition of food webs to their dynamics and properties. The intuitive interpretation that more functional diversity leads to higher resource exploitation and better ecosystem functioning was brought from plant ecology and does not apply readily to food webs. Here we appraise whether there are interpretable metrics to describe the functional composition of food webs that could foster a better understanding of their structure and functioning. We first distinguish the various roles that traits have on food web topology, resource extraction (bottom-up effects), trophic regulation (top-down effects), and the ability to keep energy and materials within the community. We then discuss positive effects of functional trait diversity on food webs, such as niche construction and bottom-up effects. We follow with a discussion on the negative effects of functional diversity, such as enhanced competition (both exploitation and apparent) and top-down control. Our review reveals that most of our current understanding of the impact of functional trait diversity on food web properties and functioning comes from an over-simplistic representation of network structure with well-defined levels. We, therefore, conclude with propositions for new research avenues for both theoreticians and empiricists.

scholarly journals Climate-induced changes in bottom-up and top-down processes independently alter a marine ecosystem

2012 ◽  
Vol 367 (1605) ◽  
pp. 2962-2970 ◽  
Author(s):  
Malte Jochum ◽  
Florian D. Schneider ◽  
Tasman P. Crowe ◽  
Ulrich Brose ◽  
Eoin J. O'Gorman
Keyword(s):  
Body Size ◽  
Body Mass ◽  
Nutrient Enrichment ◽  
Size Structure ◽  
Marine Ecosystem ◽  
Shore Crab ◽  
Top Predator ◽  
Top Down ◽  
Microalgal Biomass ◽  
Bottom Up

Climate change has complex structural impacts on coastal ecosystems. Global warming is linked to a widespread decline in body size, whereas increased flood frequency can amplify nutrient enrichment through enhanced run-off. Altered population body-size structure represents a disruption in top-down control, whereas eutrophication embodies a change in bottom-up forcing. These processes are typically studied in isolation and little is known about their potential interactive effects. Here, we present the results of an in situ experiment examining the combined effects of top-down and bottom-up forces on the structure of a coastal marine community. Reduced average body mass of the top predator (the shore crab, Carcinus maenas ) and nutrient enrichment combined additively to alter mean community body mass. Nutrient enrichment increased species richness and overall density of organisms. Reduced top-predator body mass increased community biomass. Additionally, we found evidence for an allometrically induced trophic cascade. Here, the reduction in top-predator body mass enabled greater biomass of intermediate fish predators within the mesocosms. This, in turn, suppressed key micrograzers, which led to an overall increase in microalgal biomass. This response highlights the possibility for climate-induced trophic cascades, driven by altered size structure of populations, rather than species extinction.

Bottom-up carbon subsidies and top-down predation pressure interact to affect aquatic food web structure

Oikos ◽  
2010 ◽  
Vol 120 (2) ◽  
pp. 311-320 ◽  
Author(s):  
C. L. Faithfull ◽  
M. Huss ◽  
T. Vrede ◽  
A.-K. Bergström
Keyword(s):  
Food Web ◽  
Predation Pressure ◽  
Aquatic Food Web ◽  
Top Down ◽  
Food Web Structure ◽  
Bottom Up ◽  
Web Structure ◽  
Aquatic Food

scholarly journals Latitudinal variation in top-down and bottom-up control of a salt marsh food web

Ecology ◽  
2011 ◽  
Vol 92 (2) ◽  
pp. 276-281 ◽  
Author(s):  
L. B. Marczak ◽  
C.-K. Ho ◽  
K. Więski ◽  
H. Vu ◽  
R. F. Denno ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Food Web ◽  
Latitudinal Variation ◽  
Top Down ◽  
Bottom Up

scholarly journals Alteration of coastal productivity and artisanal fisheries interact to affect a marine food-web

2020 ◽  
Author(s):  
M. Isidora Ávila-Thieme ◽  
Derek Corcoran ◽  
Alejandro Pérez-Matus ◽  
Evie A. Wieters ◽  
Sergio A. Navarrete ◽  
...  
Keyword(s):  
Climate Change ◽  
Food Web ◽  
Artisanal Fisheries ◽  
Top Down ◽  
Bottom Up ◽  
Predator Species ◽  
Marine Food Web ◽  
Productivity Decline ◽  
Marine Food ◽  
Negative Impacts

ABSTRACTTop-down and bottom-up forces determine ecosystem function and dynamics. Fisheries as a top-down force can shorten and destabilize food-webs, while climate-change driven effects can alter the bottom-up forces of primary productivity. We assessed the response of a highly-resolved intertidal food-web to these two global-change drivers, using network analysis and bioenergetic modelling. We quantified the relative importance of artisanal fisheries as another predator species, and evaluated the independent and combined effects of fisheries and plankton-productivity changes on food-web dynamics. The food-web was robust to the loss of all harvested species but sensible to plankton-productivity decline. Interestingly, fisheries dampened the negative impacts of decreasing plankton productivity on non-harvested species, while plankton-productivity decline increased the sensitivity of harvested species to fishing. Our results show that strategies for new scenarios caused by climate change are needed to protect marine ecosystems and the wellbeing of local communities dependent on their resources.

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